The disclosure relates to an electropneumatic field device, such as an electropneumatic transducer or an electropneumatic positioner, for controlling a pneumatic actuator. The actuator can for example set up, particularly control, a process flow of a processing plant, such as a refining plant, a chemical plant or a factory automation plant.
An electropneumatic field device according to the preamble of Claim 1 is known from DE 10 2010 054 878 A1. The pneumatic field device comprises an energy transducer which converts pneumatic energy into electrical energy. For this, the energy transducer has a vibratory permanent magnet which induces an electrical output voltage in a coil as an armature during a back and forth movement. The movement is initiated by means of a compressed air impulse, wherein a resetting is realized by means of a permanent magnet in the reset chamber. The armature comprises a sleeve, on the side of which facing away from the pressure working chamber, a permanent magnet is arranged. A compressed air inlet is provided on the cylinder sliding wall regions, which allows compressed air loading of the working chamber when aligned with a supply air opening in the armature sleeve, as a result of which the magnet armature is driven in one direction. Primarily in the case of longer stoppage times, it has been shown that initiating the back and forth movement of the armature was also hampered owing to increased static friction forces. Difficulties also arose in the case of the leak-tightness of the armature relative to the cylinder chamber, wherein leak-tightness is only relevant both at the compressed air inlet and the inlet opening and along the armature surfaces.